1. Field of the Invention
The present invention relates to a bit stream analyzing method and apparatus for use in a decoder circuit for a high-speed decoding of a compressed bit stream generated by way of a variable-length encoding such as a video compression and an audio compression and addition of a header information, and in particular to those which can be applied to a variable-length encoder and a stream purser having a high bit rate which requires more than speed increase of a circuit.
2. Description of the Prior Art
In a conventional compression technique for a video data and audio data, for example, the data s subjected to an arithmetic conversion and the variable-length coding, after which a header information is added, thus generating a compressed bit stream.
When analyzing a compressed bit stream thus generated through a variable-length coding and addition of a header information and decoding the variable-length code contained in the bit stream, conventionally, a single bit stream analyzing apparatus has been used for analyzing the header information and decoding the variable-length code successively. In order to increase the speed of the bit stream analysis, especially, in order to increase the speed of decoding the variable-length code, various devices have been developed on a circuit.
In the aforementioned analysis of the bit stream, in order to increase the speed of analysis of the aforementioned header information, there has been used a method to increase the processing clock and the like.
On the other hand, in the aforementioned decoding of the variable-length code, a set of processing loops are required such as insert of a bit stream into a code table, read-out of a matched code, addition to a shift amount with a barrel shifter, shift with the barrel shifter, and the like. Consequently, it is difficult to increase the processing clock, for exzample, so as to increase the speed oft he decoding processing of the variable-length code. Moreover, a variable-length code is basically a one-dimensional bit stream which should be analyzed successively starting with its starting head and cannot be processed in parallel.